Another K840CK15 Westinghouse restoration

[benman94]

Since nobody else will chime in I guess I will...

There are two possible workarounds for the 50 Meg pot that would work, though neither is particularly elegant:

First, you could always increase the values of the either the 100 Meg and 80 Meg fixed resistors, or both, and fit a new lower resistance pot to the set. Say add a 15 Meg resistor above and below the pot and buy a 20 Meg unit. You'd have to play with which side gets more fixed resistance than the other, and it would give a much smaller range to the control, but it would work.

The other, slightly better option, would be to grab a 6 to 12 position switch and build a sort of "stepped potentiometer" out of fixed resistors. A lot of audiophiles build these stepped attenuators and have great success with them in audio applications. Of course now you're limited to discrete, fixed steps, but given the fact that a 15GP22 based set rarely has anything approximating perfect convergence, I think that the stepped solution may well work. It would certainly be more reliable than any pot, and these are particularly failure prone parts.